Chemokines play an important role in immune and inflammatory responses in various diseases and disorders, including asthma, atherosclerosis and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis and multiple sclerosis. These small, secreted molecules are a growing superfamily of 8-14 kDa proteins characterised by a conserved cysteine motif. At the present time, the chemokine superfamily comprises four groups exhibiting characteristic structural motifs, the C—X—C, C—C and C—X3—C and XC families. The C—X—C and C—C families have sequence similarity and are distinguished from one another on the basis of a single amino acid insertion between the NH-proximal pair of cysteine residues. The C—X3—C family is distinguished from the other two families on the basis of having a triple amino acid insertion between the NH-proximal pair of cysteine residues. In contrast, members of the XC family lack one of the first two cysteine residues.
The C—X—C chemokines include several potent chemoattractants and activators of neutrophils such as interleukin-8 (IL-8) and neutrophil-activating peptide 2 (NAP-2).
The C—C chemokines include potent chemoattractants of monocytes, lymphocytes and neutrophils. Examples include human monocyte chemotactic proteins 1-3 (MCP-1, MCP-2 and MCP-3), RANTES (Regulated on Activation, Normal T-cell-Expressed and Secreted), eotaxin and the macrophage inflammatory proteins 1α and 1β (MIP-1α and MIP-1β).
The C—X3—C chemokine (also known as fractalkine) is a potent chemoattractant and activator of microglia in the central nervous system (CNS) as well as of monocytes, T cells, NK cells and mast cells.
Studies have demonstrated that the actions of the chemokines are mediated by subfamilies of G protein-coupled receptors, among which are the receptors designated CCR1, CCR2, CCR2A, CCR2B, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, CCR10 and CCR11 (for the C—C family); CXCR1, CXCR2, CXCR3, CXCR4 and CXCR5 (for the C—X—C family) and CX3CR1 for the C—X3—C family. These receptors represent good targets for drug development since agents that modulate these receptors would be useful in the treatment of disorders and diseases such as those mentioned above.
WO 01/25242 discloses certain thiazolo[4,5-d]pyrimidine derivatives that are useful as antagonists of receptors linked to the C—X—C and C—C chemokine families, particularly as antagonists of the CXCR2 receptor.
The present invention relates to a group of compounds that are within the generic scope of WO 01/25242 but are of a structural type not specifically exemplified therein. When compared to the Examples disclosed in WO 01/25242, the compounds of the present invention display surprisingly useful properties as antagonists of the CX3CR1 receptor.